I do not know if I use the correct words, but I do not mean balance, what I mean is that if you have 2 players exactly the same in any of its aspects, it will not be competitive since both must do exactly the same and luck will say whoever will win, not really the skill as you think.
Variety and room for improvement is what makes it competitive.
I remember some war vs war battles in which they could not kill each other or die, only the one who got tired first won.
Bookmarks